1. Field of the Invention
The present invention relates to a semiconductor element such as a nitride semiconductor laser element, to a semiconductor device incorporating such a semiconductor element, and to a method for fabricating them.
2. Description of Related Art
In many conventional semiconductor elements, a top portion of a semiconductor growth layer is formed into a ridge-like shape by etching or the like and is sandwiched between different patches of an insulating film for current constriction. This structure is generally called a ridge-like structure. A semiconductor element having such a ridge-like structure can be mounted on a mount member such as a submount, for example, with the substrate side of the semiconductor element up and thus with the opposite side thereof, on which the semiconductor growth layer is epitaxially grown, down. This mounting method is called junction-down mounting. In the fabrication of a semiconductor device, when a semiconductor element is mounted by such junction-down mounting, the ridge portion of the semiconductor element, since it is elevated, may be damaged when exposed to pressure.
As one solution to this inconvenience, there has conventionally been proposed a semiconductor device that has dummy-ridge regions formed at either side of a ridge portion (see Japanese Patent Application Laid-open No. 2000-164986). Now, this semiconductor device will be described with reference to a drawing. FIG. 15 is a sectional view of a semiconductor element having dummy-ridge regions formed thereon, shown together with a mount member, composed of a submount, a stem, or the like, on which the semiconductor element is mounted.
The semiconductor element 10 shown in FIG. 15 has a semiconductor growth layer 2 laid on the surface of a substrate 1. The semiconductor element 10 has a ridge-like portion 8 formed thereon by etching or the like, and also has dummy-ridge regions 9 formed thereon on either side of the ridge-like portion 8 in such a way that the thickness of the semiconductor growth layer 2 as measured from the surface of the substrate 1 is greater in the dummy-ridge regions 9 than in the ridge-like portion 8. Moreover, a SiO2 film 3 is laid for current constriction in such a way that different patches thereof sandwich the ridge-like portion 8, and a p-side electrode 4 is formed in such a way as to cover a portion of the surface of the semiconductor growth layer 2 around the ridge-like portion 8 as well as the surface of the ridge-like portion 8 itself.
In the mounting step, the semiconductor element 10 is fixed to a mount member with the substrate 1 side of the semiconductor element 10 up and with solder 5 laid in between. Here, the mount member is composed of a submount 6 and a stem 7. In this way, the ridge-like portion 8 is prevented from being pressed and thereby damaged. Moreover, good heat dissipation is achieved because the submount 6 is made of a high-thermal-conductivity material and the semiconductor element 10 is fixed thereto with the semiconductor growth layer 2, which generates heat, down.
The semiconductor device shown in FIG. 15 has the following inconvenience. In the semiconductor element 10, as viewed with the substrate 1 down, the surface of the dummy-ridge regions 9 needs to be made higher than the surface of the ridge-like portion 8. Thus, to form the dummy-ridge regions 9, it is necessary to perform a separate step for laying the semiconductor growth layer 2 in the dummy-ridge regions 9, or to adjust the thickness of the SiO2 film 3. This leads to an increased number of steps being required in the process for the fabrication of semiconductor elements, making the process more complex and resulting in low yields.